Regulated high voltage supplies



March 12,` 1957 ATTORNEY United States Patent-O 2,7 85,336 REGULATEDHIGH VOLTAGE SUPPLIES John A. Konkel and John Stark, Jr., Woodbury/N J.,

assignors to Radio Corporation of America, a corporation of DelawareApplicamm June, 1954, Vserial No. 435,472 6 claims. (Crais- 15) Thisinvention relates generally to regulated voltage supplies and moreparticularly to improvements in regulated voltage supplies of the typesuitable for use in satistying the high voltage requirements of acathode ray tube.

It has become more or less a general practice in the monochrometelevision art to obtain the high voltage required for the iinalaccelerating electrode of a receivers kinescope (and the voltage for thefocus electrode, where electrostatic focusing is employed) from a pulsetype supply. In such pulse type supplies, the high voltages are usuallydeveloped through rectilication of the high amplitude `transient flybackvoltage pulses appearing in the receivers horizontal output transformerduring retrace periods of theline scanning cycle, when cutoff of thehorizontal output tube causes a sudden collapse of a magnetic eld in thehorizontal deflection yoke. In color television receivers employingcolor kinescopes of the types presently contemplated, the high voltagerequirements are generally of greater magnitude, more critical as toregulation, and over all present a significantlyl more complex problemthan do the monochrome kinescope high voltage requirements. It has beenproposed to utilize a voltage regulator tube shunting the high voltageoutput of the supply applied to the kinescopes ultor electrode to insurethe desired stability of the supplied voltages. A control voltage forsuch a regulator tube has usually been derived from a high voltagebleeder, also shunting the ultor voltage output of the supply. Such ahigh voltage bleeder is generally necessary, where the color kinescopeemploys electrostatic beam convergence apparatus, to provide a tappingpoint for the derivation of the required static D.C. convergencevoltage. However, where the electromagnetic type of beam convergenceapparatus is employed, there is no need to obtain a D.C. convergencevoltage from the high voltage supply. Thus, the employment of a highvoltage bleeder for the sole purpose of obtaining a regulator controlvoltage (which need be only a small fraction of the peak supply voltage)in color receivers not using the electrostatic form of beam convergenceis wasteful of power. This has been recognized in several co-pendingapplications, namely, the application of Leonard Dietch, Ser. No.l407,921, tiled February 3, 1954 now U. S. Patent No. 2,729,764, issuedJanuary 3, 1956, and entitled High Voltage Supply, and the applicationof Bernard Vonderschmitt, Ser. No. 416,186, tiled March 15, 1954, andentitled High Voltage Supply. ln embodiments of the inventions describedtherein the control voltage for the shunt regulator of the high voltagesupply is derived from a bleeder which shunts a source of voltage of anorder substantially less than the peak ultor voltage output of thesupply, viz. a voltage of the order of the supplied focus voltage.

In accordance with an embodiment ofthe present invention a regulatedhigh voltage supplyof the type suitable for use `with a color kinescopeis provided in which the control voltage forthesupplys shunt regulatoris derivedfrom the B-boost circuit conventionally associated PatentedMar. 12,1357

With the horizontal deflection Wave output circuit of the televisionreceiver. The high voltage regulation obtained by use of such a mannerof controlling the regulator compares satisfactorily with the regulationobtained by more conventionally deriving the regulator control voltagethrough sampling the high .voltage via a high Voltage bleeder. Byrelegating the regulator sampling point to the relatively low voltageB-boost circuitry, the need for employing a high voltage bleeder insupplies for use with color kinescopes of the electromagnetic type iseliminated, thereby removing a source of significant power losses andimproving the overall eiciency of the high voltage supply. Even Wherecolor kinescopes of the electrostatic convergence type'are concerned,practice of the present invention' is advantageous in that it simplifiesthe high voltage bleeder design, making it possible to vary D.C.lconvergence with a potentiometer at a relatively low potential. Afurther advantage of practice in the present invention as compared withthe more conventional derivation of regulator control voltage from ahigh voltage bleeder has been noted with respect to a lessening inraster Width changes with line voltage variations.

Accordingly, it is a primary object of the present invention to providea novel and improved regulated voltage supply. Y

lt is a further object of the present invention to provide a novel andimproved regulated high voltage supply of a type suitable for use insatisfying the high voltage requirements of a color kinescope.

It is` an additional object of the present invention to` provide a colortelevision receiver high voltage supply in which satisfactory regulationof the supplied voltages is achieved with a saving in power losses overprior art practices.

lt is another object of the present invention to provide a colortelevision receiver high voltage supply wherein theV ing in which a highvoltage supply regulated in accordance with an embodiment of the presentinvention is illustrated schematically in Figure 1 as supplying the highvoltages required by a color kinescope in a typical color televisionreceiver.

Figure 2 illustrates schematically application of the principles of thepresent invention to regulation of another form of high voltage supplysuitable for supplying high voltages to a color kinescope in a colorreceiver of the type shown in Figure l. The color television receiverillustrated essentially in block form in Figure l is generallyrepresentative of presently contemplated color receivers for asimultaneous subcarrier type color television system in accordance withthe revised FCC color standards, and is in general accord with theprinciplesV and apparatus discussed in the article entitled Principlesand development of color television systems, by G. H. Brown and D. G. C.Luck appearing in the June 1953 issue of the RCA Review. Carrier wavesmodulated by a composite color picture signal are illustrated as beingreceived by conventional signal receiving apparatus 1l, which mayinclude the usual R. F. tuner, converting apparatus, I. F. Y

amplifier, signal detector, etc. The video frequency signals recoveredfrom the modulated carrier in the receiving apparatus 1l are ampliiiedin the video amplifier 13. synchronizing information is derived fromtheV recovered signals in the sync separator 1S and utilized tosynchronously control the Vreceivers subcarrier driveapparatus 17, tocontrol the generation of scanning Waves inthe vertical deectioncircuits 19, and control the generation (a of horizontal frequencysawtooth voltage wavesint-he horizontal sawtooth wave generator 21.

Respective color mixture signals (e. g. narrow band EQ signals and widerband Er signals, discussed in detail in the aforementioned article) arerecovered from the video signal output `of amplifier 13 in respectivecolor demodulator channels which include bandpass filters and 27 ofrespectively appropriate passbands, synchronous demodulators 31 and 33receiving respectively appropriate phases of the output of thesubcarrier drive apparatus 17, and low pass filters y355 and 37 havingthe respectively appropriate narrow and wider responses. The receiverVis also provided with a brightness channel, including a low pass filter36 having the desired wide band response, through which the Vbroad bandmonochrome portion of the composite picture signal may pass. The outputsof the brightness channel and two color channels are suitably combinedin the matrixing circuits 39 of the receiver to obtain the simultaneouscolor signals which may be applied to appropriate beam control elementsof the color imagereproducer 40.

The color image reproducer 40 is illustrated schematically as one of thethreegun, shadow-mask kinescope type. Color image reproducers of thisgeneral type are discussed in some detail in the article by i-l. B. Lawentitled A three-gun shadow-mask kinescope, appearing in the October1951 issue of the Proceedings of the I. R. E. In a color imagereproducer of this type, three electron beams are used, one for eachprimary color. The beams strike a phosphor screen composed of a regulararray of red, green, and blue-emitting phosphor dots. Between theelectron gun position and the phosphor screen there is placed a thinperforated metal sheet for the purpose of partially masking the electronbeams. The phosphor dot array on the screen comprises a plurality ofclosely spaced phosphor dot trios, each trio consisting or" a red,green, and blue-emitting phosphor dot with the centers of the dots lyingat the corners of an equilateral triangle. The trios themselves lie atthe corners of an equilateral triangle of larger size. Associated witheach of the phosphor trios is ahole in the video mask, theseholes alsobeing located at the corners of an equilateraltriangl'e. The threebeams, disposed 120 apart aboutthe tub'eaxis, are converged to a pointon the mask bysuit-a'blefstatic and dynamic beam converging means. Theelectron beam which is to contribute the red portion of Ythe'picture isprevented, by the mask, from striking thosear'ea's on the screencontaining blue and green emitting phosphors. Likewise the green andblue beams can strike only the green and blue emitting phosphor dots,respectively. The target structure S1 of the illustrative colorkinescope 40 may be considered to be of the general shadow-mask typeabove described.

As schematically illustrated the three electron beams are developed andshaped in respective electron gun structures, each including athermionic cathode 41, a control 43, a first anode or acceleratingelectrode 45, and a focusing electrode 47. The electron gun structuresmay be of the general type disclosed in the co-pending application ofHannah C. Moodey, Ser. No. 295,225, filed June 24, 1952, and disposedsymmetrically about the tube axis such as to produce three substantiallyparallel beams as in said Moodey application, or may be inclined atrespective angles to the tube axis so as to provide three beamssubstantially converging at a common point on the target, as in theco-pending application of Albert M. Morrell, Ser. No. 364,041, iiled onJune 25, 1953, now U. S. Patent No. 2,752,520, issued January 26, 1956.

A common convergence anode 49 is illustrated, which when energized bysuitable dynamic convergence waveforms developed by the generator 56along with an appropriate (static convergence) D.C. component, serves toconverge the three beams to a common .point in the plane of theshadow-mask of target structure 51 throughout the CII scanning-of theraster.Y The principles of multi-beam convergence, and a description oftypical circuits for developing dynamic convergence waveforms fromsawtooth Waves of field and line frequency may be found in an article byAlbert W. Friend appearing in the October 1951 issue of the Proceedingsof the I. R. E. and entitled Deflection and convergence in colorkinescopes. As illustrated, the dynamic convergence waveform generator5,6 may derive the respective sawtooth information from the verticaldeiiectionV circuits 19 andthel horizontal output transformer 63, andconvert these sawtooth waves into essentially parabolic waveforms, asdisclosed in the aforementioned Friend article, for combined applicationwith a D.C. component as a suitable convergence waveform to the commonconvergence electrode 49. Also, as indicated on the drawings, thedynamic convergence waveforms, generated for application to convergenceanode 49 by generator 56, may also be applied (suitably modified inamplitude) to the focus kelectrodes 27 to maintain essentially optimumfocus throughout the entire raster, as suggested in the aforementionedFriend article.

While the use of electrostatic convergence apparatus has thus beenillustrated, the alternative use of electro magnetic convergenceapparatus such as disclosed in the co-pending application Aof Hunter C.Goodrich, entitled Electromagnetic beam convergence systems fortri-color kinescopes, Ser. No. 322,653, tiled November 26, 1952, now U.S. Patent No. 2,707,248, issued April 26, 1955, in the aforesaid Morrellpatent and in another co-pending application of the Vaforesaid Morrell,Ser. No. 383,340, tiled September 30, 1953, and entitle Tri-ColorKines'cope, may be followed. In the latter the aforesaid patents andapplication, the incorporation of internal pole pieces in suchelectromagnetic 'convergence apparatus is disclosed. I

Three beam alignment magnets 57, one associated with each of the threeelectron beams may be employed to provide individual correction of beammisalignment, as disclosed in the aforementioned Friend article.However, Where electromagnetic convergence apparatus is employed of thenature providing individual control of the three beams in respectiveradial directions'relative to the tube axis, as in the aforementionedGoodrich and Morrell patents, a single beanralignment magnet providingcontrol of a selected one of the beams in a direction perpendicular tothe radial convergence control direction associated with that beam issufiiciennagain as indicated in the aforementioned Goodrich and Morrellpatents. vIn such a case the single beam alignment magnet may take theform of an adjustably insertable magnet associated with cooperating'external and internal pole pieces, as disclosed in the co-pendingapplicationV of Max Obert, Ser. No. 405,445, led January 2l, 1954, andentitled Electron Beam Control Means. Y

In addition to thebeam controlling apparatus already described, theillustratedv colo'r kine'scope 40 is also provided, as is generallycustomary, with a color'purity yoke 54, applying a uniform transversemagnetic field to all the electron Vb eam's to orient the system ofbeams as desired. The yoke `rnaycorriprise either a rotatable singlepair of coils, or two fixed pairs of coils at right angles, fed from anadjustable 'source of D. C. (as indicated on the drawing). The `use ofsuch a purity coil to deiiect the three beams equally so that they maybe adjusted to pass through their respective color centers is explainedin vgreater'det'ail vin the aforesaid Friend article. and in the'co-pending application of Friend, Ser. No. 202,185, filed December 22,1950, now U. S. Patent No. 2,719,249, issued September 27, 1955, andentitled Beam Alignment Device.

The kinescope is provided, as is'conventional, with a final acceleratingelectrode, ,the ultor 50, which may take the usual lform of a conductivecoating on the inner surface of the kine'scope 40 extending from thevicinity fiefd doublerftyge desqribed above, including vdiode 1.09.asfltheaforementionedtirstdiode, diode .113 as .theaforementionedseconddiode, .and dinde 5519 as the unidirectional coupling deviceconnectedfbetween the outputof diode 109 and .the input .of diode .113.As in the embodiment of Figure. l, thespace `discharge path of theregulator tube 69 shunts the .ultor voltage output. Again, Vinaccordance with the present invention, the .control voltage forregulator 69 fis obtained by adjustably coupling the control grid of.regulator V69 to the low voltage bleeder 75, .latter being tied between8, a point of B-ooost potential, andground.

Where the supply -of'Eigure 2 is used with a color kinescope of the`type employing electromagnetic beam convergence apparatus, as.specically considered in thea-tiere mentioned Dietch application, theyhigh voltage supply is. not required to supply a static convergencevoltage. Thus, there is no .need 4for a .high vvoltage bleeder shuntingthe `ultor voltage output of a supply. Relegation to a B-boost bleederof the derivation of the regulator-cono trol voltage "may .also obviate.the .need for the bleeder lzlillustrated in yFigure 2 as shunted acrossthe output of the first diode 109, if focus voltage is rather derivedfrom a potentiometer in the.D.-C. ycoupling path, as disclosed in theaforementioned Dietch applications. However, even where such an.output-.shunting bleeder 122 is employed for focus voltage derivationas illustrated, derivation of the regulator control voltage from aB-hoost bleeder rather than the focus bleeder 121 possesses certainadvantages apart from elimination of the high voltage bleeder 'which maybe noted. Where the focus bleeder 121 serves only focus voltagederivation purposes, the bleeder value may be selected on a basis ofhaving an optimum source impedance under design center conditions forthe ,focus supply. Also, separation of the regulator sampling operationfrom the focus bleeder circuit asssures avoidance of the rather widevariations in ultor voltage which may occur-in the dual-function use ofthe focus bleeder `circuit when focus current is appreciable.

What is claimed is:

l. VIn a cathode ray tube system .including a cathode ray tube having anultor electrode, a deection circuit including a transformer and adeection wave output tube having an electrode coupled to saidtransformer, and a damper circuit including -means -for applying aboosted supply voltage to said output `tube electrode via at leastaportionof .said transformer, a high voltage supply for developing anoperatingpotential for said ultor electrode,

said high voltage .supply comprising in combination rectifying meanshaving an input circuit and an output circuit, means for couplingsaidinput circuit to said transformer, means for deriving .said ultoroperating potential from .said outputcircuit, an electron dischargedevice including lan anode, :a cathode and a control grid, means forshunting the anode-cathode current path of said electron dischargedevice 'across said rectifying means output circuit, a low voltagebleeder connected between a point o'f 'said boosted supply potential anda point of reference potential, and means for coupling said control gridto said low Voltage bleeder.

2.111 combination with a cathode ray beam del'lection circuit includinga deflection wave output transformer, a deection wave output` tube.coupled to said transformer, and :additional means coupled to .saidVtransformer .for applying 'a boosted supply potential to'said outputtube, a` high voltage supplyrcomprising ahigh voltage rectiii'er coupledto a high potential terminal of lsaid'transformer and having an outputcircuit, voltage regulating means shurr'ting said l'outputfcrcuit, Vandmeans for controlling the operation of said voltage regulating means inaccordance with variations 'of, jsai'd 'boosted' supply potential, saidcontrolling 'means including 'a voltage divider connected between apoint of Vsaid boostedsupply .potential rinden`A point of referenceVpotential, meansrfor derivingacont .ol4 voltage from said voltagedivider, and means 4for-appli@ ing said control 'voltage to saidvoltageregulatingmeantr to vary the impedance presented by said voltageregulating means to said rectifier output circuit in accordance with thevariations of said boosted supply potential.

3..In combination with a cathoderay .bearndeflection circuit including adellection wave output transformer, a deflection wave output tubecoupled to said transformer, and additional means coupled to saidtransformer for applying a boosted supply potential to said output'tube,a high voltage supply comprising a high voltage rectifier coupled to ahigh potential terminal of said transformer and having an outputcircuit, voltage regulating means shunting said output circuit, andmeans for controlling` the operation of said voltage regulatingmeans inaccordance with variations of said boosted supply potential, saidboosted supply potential applying means including.. a damper tubecircuit shunting a portion of said trans-l former, said damper tubecircuit including a storage capacitor in series with said damper tubeandsaid transformer portion, and means for effectively adding Vthesupply potential to the charge stored by said capacitor, said voltageregulating means comprising an electron dis? charge device including agrid electrode, and saidco'ntrolling means including a voltage dividerconnectedbetween the high potential terminal of said storage capacitorand a point of reference potential, and means for coupling said controlgrid to a point on said voltage divider.

4. in a cathode ray tube system, a high voltage supply comprising incombination a transformer havingra high potential terminal and a lowpotential terminal, rectifying means coupled to said high potentialterminal and having an otput circuit, 'an electrondischarge deviceincluding an anode, a cathode, and a control grid,means..for shuntingthe anode-cathode current path of said electron ldischarge device acrosssaid rectifying means output circuit, a bleeder resistance connectedbetween said low potential terminal and a point of reference potential,and means for adjustably coupling said control grid to said bleederresistance.

5. In a color television receiver 'including a Acolor I ltinescopecomprising an ultor electrode, and including a deection circuitcomprising a deflection wave output transformer, said transformer havinga high potential terminal and a low potential terminal, said lowpotential terminal being connected to a source of boosted B+ potential,a high voltage supply for developing an ultor voltage including a highvoltage rectifier coupled to said high potential terminal -and having anoutput circuit, rneans for deriving said ultor voltage from said outputcircuit, a grid-controlled voltage regulator shunting said outputcircuit, a bleeder resistance connected between said low potentialterminal and a point of reference potential, and means for coupling saidgrid to said bleeder resistance.

6. In a color television receiver including a color kinescope comprisingan ultor electrode and a convergence electrode and including adeflection circuit comprising a deflection wave output transformer, saidtransformer having a high potential terminal and a low potentialterminal, said low potential terminal being connected to a source ofboosted B-lpotential, a high Voltage 'supply for developing an ultorvoltag'eiincluding a high voltagerectilier coupled to Said highPotential terminal and having output circuit, means for deriving saidultor voltage from said output circuit, a grid-controlled voltageregulator shunting said voutput circuit, 'a bleeder resistance connectedbetween said low potential terminal and a point of reference potential,and means for coupling said 'grid [to `said bleeder resistance, andwherein said'high 'vdltagg supply also develops a static convergencevoltagefo'r s'id of the convergence electrode 49 to the beam targetstructurev 52.V Where the ared portion of the kinescope envelope isitself a conducting metal, the conductive coating need only extendforward sufficiently to make electrical contact with the metal flaredportion.

To effect deflection of the three beams to trace a scanning raster onthe target structure 51, a deflection yoke'53 is provided withappropriately disposed horizontal and vertical deflection windings. Theyoke 53 is illustrated as having vertical yoke terminals V-V, to whichfield frequency scanning waves developed the vertical deflectioncircuits 1 9 are applied. The horizontal yoke terminals H-H derive linefrequency scanning waves from the horizontal output transformer 63,energized by a current developed in the horizontal output tube 6l toprovide the desired scanning sawtooth in the horizontal yoke. Theillustrated horizontal output transformer 63 is of the autotransformertype, the output of the horizontal output tube 61 being applied across aselected portion of the total series of windings, and the horizontalyoke being effectively coupled across a smaller segment of this portion.The driving connection of output tube 61 to the transformer 63 isillustrated as being at an intermediate point Y, while the yokeconnections are illustrated at the low potential terminal S and anintermediate point T on the transformer 63. Details of components andcircuitry conventionally associated with yoke circuits, such as widthand linearity controls, centering circuits, etc. have not beenillustrated for the sake of simplifying the drawing.

As a conventional damper tube, of well-known purpose, diode 62 isillustrated, the cathode of diode 62 being connected to an intermediatepoint W on the windings of transformer 63, and the anode of diode 62being connected by suitable means to a source of B-jpotential (notshown). In accordance with well-known power conservation principles, acapacitor 64 is coupled between the anode of damper tube 62 and the lowpotential terminal S of the transformer 63, the charge built up oncapacitor 64 in response to the periodic flow of current through damper62 effectively adding to the B-jsupply potential to provide a boostedsupply potential (i. e. a so-called B-boost potential) for the anode ofthe horizontal output tube 61 (which is D.-C. coupled via windings oftransformer 63 to terminal S).

In the illustrated high voltage supply which is regulated in accordancewith an embodiment of the present invention, the anode of a firstrectifier, diode 65, is connected to the high potential terminal Z ofthe output transformer 63. The high amplitude transient flyback pulsesappearing at terminal Z are rectified by diode 65 and provide a highamplitude D.C. potential at the diode 65s cathode, appearing across acapacitor 67 connected between the cathode and a point of referencepotential (i. e. ground in the illustrative embodiment). The outputterminal U, to which the kinescopes ultor electrode is coupled, isdirectly connected to the cathode of diode 65.

The anode of a second rectifier, diode Si, is connected to anintermediate point X on the windings of the output transformer 63. Themedium amplitude liyback pulses appearing at terminal X are rectified bydiode 81 and provide an intermediate amplitude D.C. potential at thediode 31s cathode, appearing across a capacitor 89, connected betweenthe cathode and ground. The output terminal E to which the kinescopefocus electrodes are coupled is adjustably connected via tap 91 to ableeder resistance 90 which is connected between the cathode of diode 81and ground.

` The static convergence voltage required by the convergence anode 49 ofthe kinescope 40 (beam convergence being effected electrostatically inthe embodiment illustrated in Figure l) `is obtained from a high voltagebleeder 95, which is connected between terminal U and ground, and whichin accordance with the invention is of simplified form in comparisonwith the high voltageV bleeder form required in previously discussedsupplies which use such a bleeder for regulator control voltagederivation purposes also. As illustrated, the convergence outputterminal C, to which the convergence anode 49 is coupled, is connectedto a fixed tap on the high voltage bleeder 95. Convergence voltagecontrol is effected at a low potential, as by adjusting the variable tap96 of potentiometer 97 to selectively short out a predetermined segmentof the potentiometer 97, which comprises the low potential seriesresistance portion of the high Voltage bleeder 95. The maximum potentialto which the convergence control potentiometer is subjected thus needonly correspond to the width of the desired adjustment range. Such asystem of convergence voltage control (i. e. wherein the high voltagebleeder current is varied to adjust the voltage derived from the fixedconvergence tap) is made possible through practice of the presentinvention, since such bleeder current variations can be made withoutupsetting regulation, control of the regulator tube being effected apartfrom the high voltage bleeder 95, as explained in more detail in thesubsequent paragraph.

To render the supplied voltages less sensitive to variations in loading,source voltage changes, and other such departures from normal operatingconditions, a shunt regulator tube, triode 69, is provided. The spa-cedischarge path of the triode 69 is shunted across the ultor voltageoutput of the supply, its anode being connected to output terminal U andits cathode being returned to ground via a B-isupply. In accordance withthe illustrated embodiment of the present invention, control of theregulator 69 is obtained by connecting the control grid of regulator' 69to an adjustable point on a relatively low voltage bleeder 75 connectedbetween the transtormers low potential terminal S (a point of boostedB-fpotential) and ground. The connection of the control grid ofregulator 69 to the low voltage bleeder 75 is made by means of anadjustable tap 72 on the potentiometer 73, which serves as one of theseries resistance portions of bleeder 75. Since a change in the ultoroutput voltage due to variations in loading or the like will beaccompanied by a corresponding change in B-boost potential in the samedirection, the control grid of regulator 69 will swing in a directionsuch as to appropriately alter the regulator space current to opposesuch an ultor voltage change.

Figure 2 illustrates application of the principles of the presentinvention to another form of high voltage supply suitable for servingcolor kinescope requirements, and being of the type generally disclosedin the aforementioned Dietch patent. The Dietch supply may be brieflydescribed as utilizing a modified voltage doubler circuit to obtain therequired ultor output voltage, the modification providing what may beeffectively termed a oneand-a-half voltage multiplier in whichless-than-peak amplitude yback pulses are rectified by a first diode andadded to peak amplitude iiyback pulses for rectification by a secondultor-supplying diode. In the aforesaid Dietch patent, focus voltage isderived from a potentiometer situated in the unidirectional couplingpath between the first diode output and the second diodes input. Controlvoltage for the regulator tube shunting the ultor voltage output isderived from a bleeder connected alternaf tively between either end ofthe focus potentiometer and ground. In the aforementioned Vonderschmittapplication, a high voltage supply of the general modified doubler typedescribed above is disclosed, in which, however, the focus voltage isderived as well as the regulator control voltage from such a bleederconnected between a point in the D.C. coupler path and ground, ratherthan from a resistance in that path.

The high voltage supply illustrated in association with outputtransformer 63 in Figure 2 is of the general modi- .convergenceelectrode, said high voltage supply also -in- References Cited in the leof this patent UNITED STATES PATENTS Duke Dec. 4, 1951 Grundmann June 3,1952 Little Dec. 9, 1952 Parker May 25, 1954

